Aquamate Aquarium Gravel Dark Black 2kg Provide the ultimate stylish touch to your aquarium with Aquamate Aquarium Gravel. Ph Neutral, non-toxic, and safe to use for most breeds of fish and aquarium types. Instructions: Rinse before use with a colander or strainer. Then simply place the prepared gravel on the bottom of your aquarium tow to three inches deep before filling with water. Allow for enough gravel to support any ornaments and plants!